The present invention relates to a regulating device for regulating the flow of molten metal from a metallurgical vessel wherein the device comprises a fixed refractory part and a rotatable and/or slidable movable refractory part which define cylindrical peripheral surfaces sealingly engaged with one another. The refractory parts typically comprise ceramics. However, the refractory parts may also be metallic or comprise composite materials. It is only necessary that such parts be fireproof, i.e. that they not only resist mechanically and chemically induced stresses during use but also resist stress induced by the high temperature of the molten metal with which the regulating devices are used.
Regulating devices include the one disclosed in DE-PS 35 40 202, and are characterized by the fact that they do not employ a compression device for pressing the relatively movable refractory parts together to establish an. air-tight clearance fit which prevents the penetration of molten metal. In these prior art devices it is possible, on the one hand, to actuate the regulating device with a relatively low drive force and, on the other hand, to dispose the refractory parts within the metallurgical vessel at a location at which the parts are submerged in molten metal during use. Therefore, with such a device, air is prevented from penetrating the regulating device and, in particular, air will not pass into the molten metal from the refractory parts during use.
In such a regulating device, the dimensions of an annular gap defined between the cylindrical peripheral sealing surfaces of the refractory parts is of decisive importance with respect to a satisfactory operation and life of the device. The annular gap must have dimensions which, on the one hand, allow the refractory parts to move freely relative to one another and, on the other hand, establish a tight enough clearance fit to prevent molten metal from penetrating into the annular gap. In this respect, other metallurgical parameters such as the composition of the molten metal, the wettability of the refractory parts, the temperature of the molten metal, etc. also play a role.